docs: def get_image_code(self, id_code, access_token=None, user_id=None):
          """
          Get the image of a code, by its id
          """
          if access_token:
              self.req.credential.set_token(access_token)
          if user_id:
              self.req.credential.set_user_id(user_id)
          if not self.check_credentials():
              raise CredentialsError('credentials invalid')
          return self.req.get('/Codes/' + id_code + '/export/png/url')